Wednesday, December 5, 2012

Light-up Cake

This is one of the two birthday cakes created for "Night over Erzinga" at Silk Road Rising. This was the easier of the two, but was still tricky in that it needed to have candles that were blown out onstage. Chicago has very strict rules forbidding almost all instances of live flame onstage, so real candles weren't an option. 
My solution started with a very simple circular form made of two layered circles of foam. 
In individually wired seven small yellow LED bulbs , wrapped them in tape and placed them vertically around the cake, 
then ran all the wires back to a battery and switch positioned on the back of the plate. For this part I had to be very careful to be consistent about which sides of the LED I wired to which color wire. LEDs are directional, which means that, unlike incandescent bulbs, they only work if the positive and negative sides of the battery are connected in the correct way, switch the polarity and the light will not light. When wiring one LED individually this can be an easy mistake to fix, by simply flipping the battery, when wiring many bulbs together, a mistake on one bulb would be significantly trickier to track down and correct. 
Once everything was wired I made sure everything was securely taped down to the base, and then iced over the entire thing with light weight joint compound to hide my work. 
I left the battery and the switch exposed , on the back of the cake. I later covered all but the actual button on the switch with white gaff tape so that both were accessible to troubleshooting, but less visible from a distance. 
Here it is all lit up.

To hide my ugly black tape candles I purchased a box of cheap drinking straws. I slit each straw down the side, and then wrapped it around the base of the candles.

 Each straw was cut to be a bit longer than the tape segment so that the bulb was hidden a bit inside the plastic. This helped to hide the hardware of the bulbs a bit, so that the audience saw a more believable glow instead of a bare exposed bulb.

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